The division between personal and work life often becomes blurred, especially if the person in question functions as a very public representative of the company that he or she works for. For most people, though, it is still possible to keep personal lives separate from work. However, this hasn't stopped employers from terminating workers who behave in unsavory ways off the clock. Whether this is appropriate, though, depends on the situation.
This Is Not a New Story
The idea that a worker's off-duty behavior could impact their employment isn't new. Back in the 1980s, the Harvard Business Review reported on several cases in which people had been fired due to behavior not associated with work. In some cases, the employees were reinstated after arbitration found that their behavior would not adversely impact the employer. In other cases, such as that of an employee who killed a woman, the arbitrator understandably took the employer's side.
Since then, the idea of firing someone for off-duty behavior has changed. Some states no longer allow it when the off-duty behavior was lawful (though illegal behavior is still a fireable offense). Others may fire for even lawful behavior. Florida, for example, gives employers great leeway to fire at-will (states in general have at-will employment laws, but some take it much further than others), especially if the employee knew that the behavior, even though technically legal, was prohibited. For example, Boca Raton firefighters were not allowed to smoke at all for years, even off the job, and it was a fireable offense even though smoking itself is still legal in Florida. (The union has been pushing to change the prohibition.)
At-Will, Retaliation, and More
One caution regarding at-will employment is that it is very easy for an at-will firing to look like retaliation or discrimination, which is not viewed kindly in any state. If the employee in question has been headed toward termination for a while, the employer needs to document their reasonable cause to show a paper trail, in case the employee claims the firing was a retaliatory move for some other complaint or status.
Also in question is the worker's status or classification. If the worker is a contractor, then the employer has to abide by the contract, which may have termination clauses in it that supersede at-will laws. It is also harder to claim that a contractor's lawful behavior outside of the work is grounds for terminating the contract. However, illegal behavior is another matter. Even contractors have to assume that illegal behavior could have consequences for their work.